I personally like the idea of having a place like Flickr where students and teachers can find photos to use in media projects and lessons. Having a "creative commons" area where students can search and download as well as upload and use photos or images either original or found offers many opportunities for creative projects.
Flickr could be utilized for projects such as collages. I will occasionally have a class create collages in groups to reflect a theme or idea being studied. Instead of using magazines to cut out pictures/images and then gluing to a posterboard, they can use Flickr.
I also like the Flickr tool that allows for the user to add text to an image. Being able to find photos related to a subject/theme being studied and adding text that analyzes what is viewed is a great way to make students think critically and share thoughts while doing it in a fun way.
Another project that I do with students to reinforce correct dialogue punctuation is to have them create comic strips with speech balloons or bubbles. Students could find photos to be used in a comic strip and add dialogue between characters using text right in the image.
The possibilities are endless!
Problems or obstacles that may arise might be the occasional photo found that may be questionable or inappropriate. Creating a "group" for a class to go to may help eliminate this issue. Reminding students of the "Acceptable Use Policy" signed also should discourage inappropriate use.
I am sure there are many more uses and tools that Flickr has to offer that could easily be utilized in the classroom. I look forward to exploring this site more!